Mineral oil compositions containing azulene compounds



United States Patent 3,105,820 MINERAL OIL COMPOSITIONS CONTAINING AZULENE COMPOUNDS Samuel J. Leonardi, Pitman, and Edward A. Oberright,

Woodbury, N.J., assignors to Socony Mobil Oil Compauy, Inc., a corporation of New York No Drawing. Filed June 9, 1960, Ser. No. 34,891 6 Claims. (Cl. 252-- -52) This invention relates to the art of lubrication. More particularly, it is concerned with lubricating oil compositions having improved resistance to oxidation.

As is well known, mineral lubricating oils tend to oxidize in use, especially under heat and oxidizing conditions, such as those encountered in internal combustion engines. The oxidation products formed in the oil are acidic in nature and exert a corrosive action on the metal surfaces being lubricated. The present invention is concerned with a class of chemical compounds which are highly effective in counteracting this tndency of an oil to oxidize in use and thus harm the metal surfaces.

It has now been discovered, in accordance with the present invention, that compounds containing an azulene nucleus when added in minor amounts to a mineral lubricating oil will effectively stabilize the oil against the deleterious effects of oxidation. It is, therefore, the primary object of this invention to provide mineral lubricating oil compositions of improved oxidation stability, said compositions containing minor amounts of azulene compounds. Other and further objects will be apparent from the following description of the invention.

Azulene compound-s in general are contemplated in the invention. A preferred class, however, are those represented by the formula:

wherein R may be hydrogen in all instances (azulene) or in one or more instances a substituent group selected from alkly, aryl, alkaryl, aralkyl and alkoxy groups. The number and variety of the said substituent groups, or the molecular weight thereof, is not critical from the stand point of the suitability of the compounds for use in the invention, the choice of a particular compound being chiefly a matter of its availability and/ or cost of manufacture.

Non-limiting examples of azulene compounds suitable for the invention are the following:

Cyclopentacycloheptene (azulene) 2-isopropyl-4,8-dimethylazulene (vetivazulene) 3,8-dimethyl-5-isopropylazulene (guaiazulene) 2-isopropyl-S-methylazulene 1,3,5-trimethy1azulene 1,3,5-trimethoxyazulene 2-ethyl-8-methoxy-4-methylazulene 2-ethy1-4-methylazulene Z-phenylazulene 2-(octylphenyl)-azulene S-benzylazulene 5-isopropylazulene Z-ethylazulene 2-laurylazulene S-octadecylazulene 6-naphthylazulene Patented Oct. 1, 1963 ICC Further information relative to the various azulene compounds and their preparation may be obtained by reference to the article entitled The Azulenes, by Maxwell Gordon, Chemical Reviews, vol. 50, pp. 127-200 (1952) V ANTIOXIDANT ACTION The effectiveness of the azulene compounds contemplated herein as oxidation inhibitors for mineral lubricating oil has been demonstrated by oxidation-stability tests conducted on mineral lubricating oil alone and on the same oil blended with small amounts of representative azulene compounds. For purpose of comparison, naphthalene, the common benzenoid isomer of azulene, was also tested. The tests were conducted in an oxidations-tability apparatus, essentially the same as that described by Larsen et al., Industrial and Engineering Chemistry, vol. 34, pp. 183-193 (1942), as follows. The test oil is maintained at 300 F. while pure oxygen is recycled therethrough in a closed system. Gaseous oxidation products which are formed are removed by suitable adsorbents in the system in order to maintain the purity of the oxygen during the test. As oxygen is taken up by the oil, the corresponding pressure drop activates a solenoid valve which admits make-up oxygen in fixed increments which are recorded on a time chart. A record of the quantity of oxygen with which the oil has been reacted is thus available at any given'time. The results are expressed in terms of the time required for the oil sample to absorb a given amount of oxygen.

The base oil used in the tests was a solvent-refined mineral lubricating oil having a Saybolt Universal viscosity of 54 seconds at 210 F. and 368 seconds at F. The test results are given in Table I.

It will be observed from the test results that both of the azulene compounds were highly efiective in reducing the oxidation of the oil. On the other hand, the naphthalene was not significantly effective.

The azulene compounds of the invention may be used in lubricating oil in amounts ranging from about 0.01 to about 10 weight percent, depending upon the particular oil to be improved and the application for which it is designed. For most purposes, however, the use of from about 0.5 to about 3.0 percent of the additive is sufiicient to provide the desired improvement.

The azulene compounds may be used in lubricating oils along with other addition agents designed to impart different improving properties to the oil, such as deter gents, V.I. improvers, pour point depressants, anti-foam agents, anti-rust agents, extreme pressure agents, etc.

Although the invention has been illustrated herein by means of certain specific examples and tests, it is not intended that the scope of the invention be limited thereby, but only as indicated by the following claims.

We claim:

1. A mineral lubricating oil containing a minor amount,

suflicient to inhibit said oil against oxidation, of an azulene compound of the formula:

wherein R represents a radical selected from the group consisting of hydrogen, alkyl, aryl, alkaryl, aralkyl and alkoxy radicals.

2. A mineral lubricating oil containing a minor amount, sufiicient to inhibit said oil against oxidation, of azulene.

3. A mineral lubricating oil containing a minor amount, sufiicient to inhibit said oil against oxidation, of 3,8-dimethyl-5-isopropylazulene.

4. A mineral lubricating oil containing a minor amount, sufficient to inhibit said oil against oxidation, of 1,3,5 trimethoxyazulene.

5. A mineral lubricating oil containing a minor amount,

5 sufiicient to inhibit said oil against oxidation, of 2-pheny1- azulene.

6. A mineral lubricating oil containing a minor amount, sufficient to inhibit said oil against oxidation, of 2-is0- propyl-4,8-dimethylazulene.

References Cited in the file of this patent UNITED STATES PATENTS 2,217,173 Lincoln et al. Oct. 8, 1940 15 2,629,750 Rath Feb. 24, 1953 2,766,304 Ziegler et a1. Oct. 9, 1956 

1. A MINERAL LUBRICATING OIL CONTAINING A MINOR AMOUNT, SUFFICIENT TO INHIBIT SAID OIL AGAINST OXIDATION, OF AN AZULENE COMPOUND OF THE FORMULA: 